If you want to purchase an iPhone from an Apple Store, forget about using cash or a gift card.

Apple is stepping up its efforts to limits resellers from getting their hands on the popular iPhone. Apple wants to crack down on those who buy, unlock and then resell iPhones to consumers.

Of the roughly 1.4 million iPhones that have been sold since its introduction in late June, Apple COO Tim Cook estimates that 250,000 iPhones have been purchased by customers who have the intention of unlocking the phones.

"Customer response to the iPhone has been off the charts, and limiting iPhone sales to two per customer helps us ensure that there are enough iPhones for people who are shopping for themselves or buying a gift," said Apple spokeswoman Natalie Kerris. "We're requiring a credit or debit card for payment to discourage unauthorized resellers."

Today, however, Engadget is reporting that Apple has gone one step further than just denying cash customers. Apple is also denying the use of Apple Gift Cards to purchase iPhones. For those looking to get a stack of Apple Gift Cards for Christmas to put towards the purchase of an iPhone; you may want to rethink that idea.

Apple recorded 67 percent higher profits for Q3 2007 thanks in part to the iPhone. Apple's crackdown on resellers and those who wish to unlock the iPhone is no doubt a measure to protect the steady cash flow from AT&T.

According to Piper Jaffray analyst Gene Munster, AT&T is paying Apple an average of $18 a month for each iPhone customer. In other words, Apple receives $399 for each iPhone sold plus an additional $432 over the course of a two-year contract thanks to AT&T's exclusivity arrangement.

"It looks like the iPhone 4 might be their Vista, and I'm okay with that." -- Microsoft COO Kevin Turner